Heels with nail-holding fillers



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HEELS WITH NAIL-HOLDING FILLERS Filed Dec. 31, 1958, Ser. No. 784,159

3 Claims. (Cl. 36-40) This invention relates to a light-weight rigidheel with a nail-holding filler.

The fashion-dictated high thin heelsfor womens shoes have necessitatedthe use of strong rigid materials which do not break easily, such asrigid plastic or light-weight meta-ls. Metal is not nailable andheretofore awkward and expensive procedures have been required forattaching metal heels. Serious problems arise also in effectingattachment of solid plastic heels by nailing.

It has been proposed to provide the plastic heels with wooden insertsfor heel attaching with nails. The proposals have relied on a forcefitted or adhesively bonded plug or on molding the heel material aroundthe insert to embed it. In these structures it was necessary to use awooden insert or plug extending well outside of the heel attachingnailing pattern since the surrounding plastic would not hold nails.Moreover, accurately sized inserts were required for inserts to be forcefitted or adhesively secured in preformed heels.

It is an object of the present invention to provide a novel light-weightheel with a heel-seat engaging surface which permits a shoe upper to beeasily and firmly attached by nails or screws.

According to the present invention, a heel member of light-Weight rigidmaterial in the shape of a heel but having a cavity in the heel seatengaging portion is provided with a nailable insert which is held infixed position in the heel-seat engaging surface and in spacedrelationship to the walls of the recess by a hard, nailable adhesiveresinous composition. A satisfactory bond is thereby provided betweenthe interior wall of the heel and the insert. The hardened combinationof the insert and resinous composition is machineable for shaping to thecontour of a shoe upper and accepts and holds nails used in heelattaching. In another aspect of the invention, the heel is provided witha nailable attaching surface provided by the adhesive resin compositionalone.

The invention may be better understood with reference to theaccompanying drawings, in which Fig. l is an exploded view inperspective With parts broken away of the heel seat end of a shoe upperand a heel; and

Fig. 2 is a perspective view of a nailable insert which may be used inthe heel of the present invention.

The heel member as shown in Fig. 1 is formed with a cavity 12 in itsupper portion which is filled with a nailable body 14 held centered inthe cavity 12 by a resinous mass 16 adhering to the walls 18 along thesides 20 and back 22 of the cavity 12. 'In the heel 10 the cavity 12 isgenerally wedge shaped and is defined by a cavity base surface 24- Whichmay be substantially flat, extending from the heel breast 26 to a shortdistance from the exterior surface of the heel at the sides 20 and back22. Portions of the heel member 10 above this cavity base surface 24 arereduced to a shell or wall 18 which may be of substantially uniformthickness or may be provided With reinforcing thickened portions, suchas the ribs 28 t t, j

extending along the interior faces of the wall 18 parallel to the cavitybase surface 24. The rim or upper edge 30 of the wall 18 is preferablyrelatively thin, particularly where the heel member is made of a metal,in order to simplify concaving problems.

Considerable variation is permissible in the shape and size of thecavity 12 subject to the limitation that the cavity must have a minimumoutline at least slightly larger than the heel-attaching nailing pattern32 of the shoe upper 34 with which the heel is to be used, as shown alsoin Fig. 1. Also the depth of the cavity 12 within this outline mustbegreat enough to receive the portions of the heel attaching nails 36projecting through the heel seat 38 of the shoe upper 34 in thepredetermined pattern corresponding to that shown at 32 on the exposedtop cross section 40 of the insert 14. It is also important that thewalls 18 of the heel member surrounding the cavity 12, that is, thematerial of the heel member between the interior walls of the .cavityandthe exterior of the heel member have sufficient thickness to withstandthe stresses imposed on the heel when attached to a shoe.

The heel member 10 is made in the desired heel style from a light-weightbut rigid material which may be a rigid plastic, such as celluloseacetate butyrate, cellulose acetate, nylon, styrene, or acrylate resin,or a cast lightweight metal, such as aluminum or magnesium. The nailablebody 14 is held in fixed position in the heel cavity 12 in spacedrelation to the walls of the cavity 12 by a resinous mixture 16comprising a thermosetting resin, a curing agent for the resin, and aselected inert material which is filler and thickener for the resin.This composition, when cured, is adhesive to both the nailable body 14and the metal or plastic surfaces of the heel member 10, and is hardenoug'hto be machineable. It also may be compressed sufliciently by theentering nails to retain them without splintering, since the resinmaterial does not sufficiently penetrate the individual particles offiller to render them rigid.

The curing type resin used for the present invention is stronglyadhesive to both the 'nailable body 14 and the metal or plastic of theheel member 10 and possesses a cured strength which will endure futuremachining. A preferred thermosetting resin is a polyepoxide resin (fluidat room temperature) which is a resinous glycidyl polyether of a memberof a group consisting of polyhydric phenols, polyhydric alcohols andmixtures of these. The polyepoxides are complex resinous materials andmay be produced by the reaction of polyhydric phenols with apolyfunctional chlorohydrin such as epichlorohydrin and glycerolchlorohydrin. The preparation of epoxide resin is shown in United StatesLetters Patent No. 2,506,486 to Bender et al., granted May 2, 1950, andNo. 2,589,245 to Greenlee, granted March 18, 1952.

The preferred epoxide resins used 'in the present invention are thoseliquid at room temperature, to facilitate mixing, with a viscosity at 25C. of from about 3600 to 15,000 c.p.s. However, normally solid epoxides,which may be liquefied by gentle heating, may be used. The range ofepoxy equivalents is from about to 210, and the molecular weight isbetween 340 and 400. Such epoxy resins are commercially available asEpon 820 and 828, made by the Chemical Division, Shell Oil Co. andAraldite 6005, made by the Ciba-Co., Inc.

The curing agent for the epoxide resin is preferably a fluid polyamideresin, but other curing agents, such as amines, may be used with theaddition of a fiexibilizer or aplasticizer. Useful polyamidcs forcombination with the epoxy resin are .the products obtained by reactingpolymerized polyene fat acids or their amide forming derivatives, suchas their monohydric alcohol esters or their anhydrides or acyl halides,with an organic a1iphaticcompound possessing at least two primary aminogroups. The polymeric fat acids may be those formed for example bythermal polymerization of drying or semi-drying type fatty oilscontaining glycerides of polymerizable fat acids such as soybean oil,linseed oil, cottonseed oil, perilla oil, dehydrated castor oil and thelike. The polymeric glyceride may then be isolated as by distillationand converted to polymeric fat acid by hydrolysis.

The polymerized fat acids, esters or anhydrides are combined withpreferably equimolecular amounts of amino compounds such as ethylenediamine, diethylene triamine, hexamethylene diamine, tetraethylenepentamine or other alkylene polyamines, or mixtures of these with eachother or with related compounds such as monoethanolamine. Thecombination reaction is brought about by heating the mixed materials atsuch a temperature that polyaminolysis of the fat esters or dehydrationof the polyamine salts of the fat acids will occur readily. Temperaturesof 150-175 C. for a few hours with an increase to l75225 C. for 20 to 40minutes just prior to removal of, polyamide from the reaction chamberare sufiicient. The time and temperature will vary depending on thematerials used and the type of product desired. Details of this resinforming process may be found in United States patent to Oowan et al.2,450,940 of October 12, 1948. Such a polyamide resin is Versamid 125, aproduct of the General Mills Chemical Division.

When fluid polyamide resins are blended with liquid epoxy resins thereaction between the amino groups of the amides and the epoxy groups ofthe epoxies results in a three-dimensional polymer on completion of thereaction.

The ratio of epoxy to polyamide is adjusted to produce a compositionadhesive but not too brittle. This is best obtained with a ratio byweight of from 50 epoxy to 50 polyamide to 60 epoxy to 40 polyamide.However, a wider range from 40 to 70 epoxy to 60 to 30 polyamide may beused. Too much epoxy yields a product too brittle; on the other hand,too high a percentage of polyamide makes a rubbery mixture.

The primary filler, which also acts as a thickening agent for the resin,may be selected from a variety of inert compressible fibrous materials,such as wood flour or ground walnut shells. Usable material for theprimary filler should have a bulk volume not over 3.9 ccs./gm., and itis preferred to be about 2.3 ccs./gm. A preferred filler is ENE-100,Solka Floc, an a-cellulose product from the Brown Company. It has afineness of 100 mesh.

The primary filler, such as the wood flour, is used to the extent offrom about to about 35 parts by weight based on the Weight of the resin,but the preferred percent is about to 25 parts by weight based on theweight of the resin. The upper limit is determined by the difliculty inmolding.

If it is desired to modify the hardness or strength of the compositionfor reinforcement purposes, there may be added in addition small amountsof mineral fillers, i.e., up to 10% by weight, based on the weight ofresin used.

The combination of filler and resin, particularly if it is to be usedwithout the addition of a wood insert, should be selected so that thefiller is not permeable to the resin, i.e., does not have its poresfilled by the resin. This preserves to some extent the compressivequality of Wood itself, which allows attaching nails or screws to begripped by the penetrated surface.

The nailable insert 14 is preferably of wood but other nailablematerials such as compressed fiber blocks may be used. The insert has anupper face 40 of suitable size and shape to receive heel attaching nails36 in a predetermined pattern, and also has a depth sufficient to acceptportions of the nails extending through the heel seat 38 of a shoe upper34 the nail pattern 32.

The over-all dimension of the insert 14 must also be small enough toallow the insert to fit within the cavity 12 with its side walls inspaced relationship to the walls 18 of the heel member 10, the spacebetween the walls and insert being filled with the nailable resinousmixture. It is to be observed that by reason of the nailable characterof the mixture in the spaces and the strong bond between the mixture andboth the insert and the walls of the heel member, the minimiumdimensions of the insert are not critical, although the insert does havegreater nail holding power than the resinous mixture.

The hardwood insert 14, shown in Fig. 3, is conveniently prepared bycutting to size from a 1% diameter dowel, preferably of maple. Dependingupon the size of the heel, the over-all length may vary from 1% to 1/2". One end 42 is cut perpendicular to the dowel length; the other iscut at an angle selected so that the face 40 of the insert, when inposition, is generally in line with the rim 30 of the heel seat, forinstance, at an angle of about 45. The angle of the wood grain providesoptimum nail holding ability and minimum danger of splitting.

A predetermined amount of moldable resin mixture 16 is deposited in thecavity :12 of the heel form 10. The wood insert 14 is centered andpressed into the resin mixture 16, forcing it down into the cavity 12 ofthe heel 10 to surround the insert 14 up to the level of the rim 30.

It is to be understood that the resin filler 16 may be used without thewood block insert by filling the cavity 1'2. of the heel 10 so that thesurface at the attaching face 44 is level with the heel rim 30.

After the heel is filled with the resinous mixture or the combinationresinous mixture and dowel insert, the resin is allowed to cure at roomtemperature overnight. Alternatively, a rapid cure may be effected byheating the freshly assembled heel shell and filler at a temperature of190 F. for one hour.

After curing and cooling, the resinous mixture 16 is hard and firm andstrongly adhesive to the walls of the heel 10. The wood insert 14 isheld firmly in position. The hard filler combination is then machined byconventional procedure to a concave surface suitable for attachment to ashoe upper.

The following examples are given to aid in understandthe presentinvention. It is to be understood that the invention is not limited tothe specific composition and procedure here described:

Example 1 Parts by weight Epoxide resin (Epon 820) 454 P-olyamide resin(Versamid 125) 303 Wood flock, 100 mesh (Solka Floc BNBl00) 151 Theepoxide resin was a glycidyl polyether liquid at room temperature withviscosity at 25 C. of 4,000 cps. to 14,000 cps, and an average molecularweight of 350 to 400. Reactivity range of epoxy equivalents are 175 to210.

The polyamide resin was also fluid at room temperature with a viscosity,measured by a Brookfield viscometer, #6 spindle 4 rpm, at 40 C., of to120 poises and at 23 C. of 500 to 550 poises and a specific gravity of0.97. 'It had an amine value ranging from 290 to 320.

The filler used was an OC-CfilllllOSB wood flock of mesh.

The polyamide resin was added to the fiuid epoxide resin and thecombination was quickly and thoroughly mixed. With continued stirring,the wood flour was slowly and evenly added, the mixture increasinglythicken mg.

This putty-like mixture was spread in the cavity 12 in the heel-seatface 44 of a thin, high aluminum heel 10, levelly supported. A maplewood block #14 with a bottom 42, a long side 46, and the face 40 cut atan angle of 44, was centered and pushed evenly into the soft resinmixture 16, the block-face 40 being held parallel with the heel-seatface 44, and the edge 48 extending into the cavity 12 toward the back 22of the heel. The face 40 of the block 14 was exposed so that the frontend 5b was toward the heel breast 26 and the top edge 52 toward the topback 54 of the heel 10. The resin mixture 16 was forced down toward thebottom of the cavity 12 and the top surface of the mixture rose evenwith the rim 30 of the heel.

The supported shell with its combination filler was put aside to cureovernight at room temperature.

The cured heel was a unitary structure with the cured resin mixture 16firmly holding the wood block 14 centered in the heel face 44, andstrongly united in turn to the walls of the cavity 12 in the heel. Theattaching face of the heel, composed of the resin and embedded block,was concaved by conventional machinery for cooperation with the heelseat of a shoe upper.

The finished heel was easily and firmly attached to the correspondingupper by nailing into the face 44 of the wood insert 14 in a definitepattern 32, as shown, The nails 36 extended through the heel seatengaging face 38 of the overlasted shoe upper 34 and penetrated throughthe face 46 of the insert 14. The combination filler had an excellentholding power of 173 pounds.

Example 2 A similar aluminum heel was filled with the resin mixtureuntil the mixture was level with the heel rim 30, the wood insert beingomitted. After curing, the composition was concaved. When nails wereused in joining heel to upper, the resin composition was found to havenearly the same holding power.

It is to be understood that this invention is not limited to anyparticular style, size or shape of heel and may be employed for a heelshell of other rigid material than the metal heel shell hereindescribed.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent of the United States is:

l. A heel for a shoe comprising a rigid lightweight heel member havingits upper portion formed with a cavity of an area and depth to receiveportions of heel attaching nails extending through the heel seat of ashoe in the heel attaching nailing pattern, said cavity being defined bywalls flaring outwardly and terminating in relatively thin upper edges,leaving the top of said heel unobstructed to receive heel attachingnails over substantially its entire area, an insert of nailable materialshaped to fit within said cavity having an upper face of size and shapeto extend outside said heel attaching nailing pattern to receive andhold heel attaching nails, and a body of cured hard nailable resinouscomposition filling spaces between the walls of said cavity and saidinsert, and serving as the exclusive means to hold said insert in fixedrelationship to the walls of said cavity, and the exposed surfaces ofsaid curved resinous composition and said insert having a shape to fitagainst the heel seat of a corresponding shoe upper.

2. A heel for a shoe comprising a rigid lightweight metal heel memberhaving its upper portion formed with a cavity of an area and depth toreceive portions of heel attaching nails extending through the heel seatof a shoe in the heel attaching nailing pattern, said cavity beingdefined by walls flaring outwardly and terminating in relatively thinupper edges, leaving the top of said heel unobstructed to receive heelattaching nails over substantially its entire area, a wood insert shapedto fit within said cavity, said insert having an upper face cut at anangle of approximately 45 to the grain of said wood, and of size andshape to extend outside said heel attaching nailing pattern to receiveand hold heel attaching nails, and a body of cured hard nailableresinous composition comprising a mixture of a cured thermosetting resinand a compressible fibrous material filling spaces between the Walls ofsaid cavity and said wood insert, and serving as the exclusive means tohold said insert in fixed relationship to the walls of said cavity, andthe exposed surfaces of said cured resinous composition and said woodinsert having a shape to fit against the heel seat of a correspondingshoe upper.

3. A heel for a shoe comprising a rigid lightweight metal heel memberhaving its upper portion formed with a cavity of an area and depth toreceive portions of heel attaching nails extending through the heel seatof a shoe in the heel attaching nailing pattern, said cavity beingdefined by walls flaring outwardly and terminating in relatively thinupper edges, leaving the top of said heel unobstructed to receive heelattaching nails over substantially its entire area, a wood insert shapedto fit within said cavity, said insert having an upper face cut at anangle of approximately 45 to the grain of said wood and and of size andshape to extend outside said heel attaching nailing pattern to receiveand hold heel attaching nails, and a body of a cured mixture of anepoxide resin and wood flour filling spaces between the walls of saidcavity and said insert, and serving as the exclusive means to hold saidwood insert in fixed relationship to the walls of said cavity, and theexposed surfaces of said cured resinous body and said wood insert havinga shape to fit against the heel seat of a corresponding shoe upper.

References Cited in the file of this patent UNITED STATES PATENTS1,336,194 Burger Apr. 6, 1920 1,609,918 'Perugia Dec. 7, 1926 1,710,378Owen Apr. 23, 1929 1,781,931 Owen Nov. 18, 1930 2,871,583 Cooper Feb. 3,1959 FOREIGN PATENTS 484,627 Great Britain May 9, 1938

